Remember, you can only book 11 months out with the points from that property. If you add 50 points to BLT or AKV, then you could book those 50 points at BLT or AKV 11 months out.
My opinion: If you have enough points at SSR for anything you think you might want to reserve 11 months out, then go ahead and add on at a different property. Figure out the most points you would use at SSR, taking banking and borrowing into consideration, then make your decision.